The detection of the organic extractables in a biotech product by liquid chromatography on-line with electrospray mass spectrometry.

We illustrated the ability of electrospray mass spectrometry (MS) to identify extractables from stoppers in biotech products. The advantages of using electrospray mass spectrometry (MS) as compared to the use of other traditional methods were also demonstrated, particularly, the capability of detecting the extractables from the mixtures of a peptide drug with its formulated excipients. MS alone could detect the antioxidant extractable, Butylated Hydroxytoluene (BHT), to the 0.5 ppm level. By using liquid chromatography (LC) on-line with MS, the detection of BHT improved at least to 0.1 ppm, depending on the LC column dimensions and injection volumes. Following aqueous buffer extraction, there were no detectable extractables nor chemical modifications of the peptide drug. When acetonitrile was used as the extraction solvent, we detected trace amounts of BHT (0.14 to 1.7 ppm) and a polymer with a molecular weight of 355 plus 44 mass unit extensions from the stopper. This unexpected polymer coeluted with BHT in LC could not be detected without on-line with MS. This incidence of coelution proved that the multidimensional approach, LC on-line with MS, is a powerful tool to characterize the extractables from the stopper and at the same time to assure the integrity of the drug substance.